July 30, 2015

Dilution or amplification?

Variable data

Civitello et al. 2015

Publication time series

Challenges and opportunities

  1. Linking existing theory and data
  • Competence, extirpation risk, and life history

Competence, extirpation risk, and life history

Competence, extirpation risk, and life history

Competence, extirpation risk, and life history

Challenges and opportunities

  1. Linking existing theory and data
  • Competence, extirpation risk, and life history
  • Modes of transmission

Modes of transmission

Frequency vs. density-dependent

Modes of transmission

Frequency-dependent (FD) vs. density-dependent (DD) vs.

Constant risk:

\(\dfrac{dI}{dt} = \beta S\)

Power law:

\(\dfrac{dI}{dt} = \beta S I^q\)

\(\dfrac{dI}{dt} = \beta S^p I^q\)

Negative binomial:

\(\dfrac{dI}{dt} = (kS) log(1 + \frac{\beta I}{k})\)

Modes of transmission

Theory

Little known beyond FD and DD transmission

Modes of transmission

Theory

Little known beyond FD and DD transmission

Data

Suggests support beyond FD and DD

(i.e. 'non-linear' transmission functions)

(Orlofske et al. in prep)

Challenges and opportunities

  1. Linking existing theory and data
  • Competence, extirpation risk, and life history
  • Modes of transmission
  • Competition (among hosts and parasites)

Among host competition

Effect of richness depends on interaction between competition and transmission

Strauss et al. 2015

watch for O'Reagan et al. in press AmNat

Among parasite competition

Theoretical gaps

Multi-host, multi-parasite systems:

  • interaction between host and parasite diversity?
  • role of competition?
  • evolution and diversity?
  • mathematical tractability?

Challenges and opportunities

  1. Linking existing theory and data
  • Competence, extirpation risk, and life history
  • Modes of transmission
  • Competition
  1. Extending the framework
  • Biodiversity and symbionts

Biodiversity and symbionts

Most processes non-specific to parasites

  • how does host diversity affect symbiont diversity?

Biodiversity and symbionts

Similar to habitat area-heterogeneity trade-off in free living species

Biodiversity and symbionts

Role of parasitism vs. mutualism

Empirical evaluation

San Francisco Bay Area amphibian parasites

Why symbionts in general?

  • More data
  • Many parasites are facultative
  • Broader class of species interactions
-/- -/0 -/+
0/0 0/+
+/+

Challenges and opportunities

  1. Linking existing theory and data
  • Competence, extirpation risk, and life history
  • Modes of transmission
  • Competition
  1. Extending the framework
  • Biodiversity and symbionts
  • Scale transitions

Scale transitions

Local dynamics

Scale transitions

Local dynamics \(\rightarrow\) regional dynamics

Scale transitions: theoretical results

Local dynamics \(\neq\) regional dynamics if

  • local dynamics are non-linear
  • densities vary spatially
  • conditions vary spatially

(Chesson et al. 2005)

Temporal scale discrepancies

Most theory (but see Roche et al. 2012): short term

  • instantaneous rates
  • \(R_0\)
  • force of infection

Most data: long-run

  • prevalence
  • seroprevalence
  • density of infected hosts

Challenges and opportunities

  1. Linking existing theory and data
  • Competence, extirpation risk, and life history
  • Modes of transmission
  • Competition
  1. Extending the framework
  • Biodiversity and symbionts
  • Scale transitions

Closing thoughts

Acknowledgements